This invention relates to an air-fuel mixture control valve assembly for automotive vehicles and more particularly, to a valve assembly for the regulation of the air-fuel mixture delivered to an internal combustion engine of automotive vehicles.
It has been required, by imposed regulations for automotive vehicles, to prevent misfiring and accompanying increase in the amount of unburnt, harmful constituents present in exhaust gases. More specifically, the regulations specify the maximum permissible amounts of various pollutants including carbon monoxide, hydrocarbons and nitrogen oxides which may be emitted by the engine exhaust gases into the atmosphere.
One of the solutions for the emission control problem is to employ an air-fuel mixture control valve assembly which introduces atmospheric air into the intake manifold upon a predetermined condition of driving. That is, when sudden deceleration is applied to rapidly increase the negative pressure in the intake manifold, the unburnt fuel adherent on the inside wall of the intake manifold may be introduced into the carburetor to cause a temporary richness of the mixture which, in turn, results in the generation of carbon monoxide and hydrocarbons.
The mixture control valve assembly has been proposed to avoid such temporary mixture richness by air admission into the intake manifold. The valve assembly comprises a valve member which will control the opening-closing of the air admission passage in response to the driving conditions and a one-way ball valve disposed in the air admission passage to thereby prevent possible adverse current of a high pressure and high temperature fluid due to backfiring which may be caused by, for example, wrong spark timing.
The one-way ball valve has, however, disadvantages in that the ball has to be seated due to the adverse current pressure of fluid against the weight of the ball thereby resulting in inferior response of movement thereof and insufficient prevention of the adverse current.